The invention relates to a variable exhaust gas turbocharger for an internal combustion engine including an exhaust gas turbine and a compressor disposed within a housing. The compressor wheel is connected to an exhaust gas turbine wheel via a shaft. The compressor has a variable guide vane arrangement and/or throttle device.
A variable exhaust gas turbocharger is already known for example from DE 199 55 508 C1. An internal combustion engine with an exhaust gas turbocharger which comprises an exhaust gas turbine and a compressor for generating compressed charging air is described. In addition, the internal combustion engine has a turbine which is rotationally connected to the compressor and to which combustion air can be fed via an adjustable shutoff element. The turbine outlet is connected to the intake section downstream of the compressor via a connecting duct. The internal combustion engine has a closed-loop and open-loop control unit for generating control signals which adjust the shutoff element.
A supplementary duct which branches off from the intake section upstream of the compressor, to the air inlet of the turbine, is provided. The air supply into the supplementary duct and into the compressor inlet can be adjusted by means of the shutoff element. In the lower load range, an actuating signal, by means of which the shutoff element can be adjusted to a position which opens the supplementary duct and reduces the air supply to the compressor inlet can be generated in the closed-loop and open-loop control unit if the set-point charging pressure drops below a threshold value.
Variable exhaust gas turbocharger turbines are currently being used in relatively small internal combustion engines and in relatively large utility vehicle diesel engines which operate with a medium speed.
The possibilities of the use of variable inflow guide vanes as a swirl device upstream of the compressor wheel and of diffusers with variable vanes downstream of the compressor wheel on the widespread mixed flow compressors have been known for a long time. The mixed flow compressors have an axial flow at the inlet and a radial flow at the outlet. Hitherto, variable inflow guide vanes have been used in relatively small numbers, which is due in particular to the complicated and expensive design of the axial inflow guide vane structures.
It is the object of the present invention to provide an exhaust gas turbocharger in such a way that the guidance of the flow is improved and the efficiency of the exhaust gas turbocharger increased by means of guide devices which are installed in to the flow passage.